The present invention relates to an improved coating system and to the method for applying it to surfaces where long term protection from exposure to adverse environmental conditions is required. The metal surfaces of food processing plants, for example, demand coatings which do not crack and flake. Another application for a flexible coating is the protection of automobile body surfaces, where the sheet metal parts are subject to attack by the salt applied to road surfaces for ice removal. Presently available rust protection and rust-prevention techniques, while helpful, leave room for considerable improvement. Automobiles are a particularly common problem, and considering the high cost of these products, a long-term reliable rust prevention treatment would be highly desirable and useful.
The method of the present invention includes the utilization of first and second films which are applied sequentially over the surface to be protected, and the resultant composite film is one which has been found to be highly desirable from the standpoint of preventing and/or resisting corrosion and/or rust formation. The combined films are both adherent and coherent, and form a tough composite film which remains flexible under normal ambient conditions. The composite film provides good bond strength, as well as good peel strength characteristics. Generally, the present invention utilizes a coating system comprising a pigmented primer and a flexible pigmented top coat, which provides a composite system which protects the surface of ferrous metals from attack by salt, humidity and the ambient. The preferred application technique for both films is by pressurized spraying, although other application techniques may be employed if desired.
In the protection of surfaces from environmental and/or ambient conditions, the utilization of tough flexible films is desirable. It occurs, however, that if a film is to be rendered extremely tough and durable, it may lack certain flexural characteristics. As a result, such films may have a tendency toward chipping and/or cracking whenever the substrate is subjected to unusual flexure. If the toughness is to be sacrificed, then the films tend to be less impervious and more susceptible to mechanical damage, and hence may be more likely to chip and/or fracture when exposed to unusual mechanical forces.
Surface protecting films are normally formulated and/or provided with a variety of physical and/or chemical properties as goals or objectives. Specifically, such properties as adhesion, cohesion, bond strength, peel strength and toughness are all highly desirable. Generally, these properties are desirable, and are normally increased whenever possible. As it turns out, however, certain of these properties may be increased only at the expense of others, and hence lie at cross-purposes, one to another. Therefore, one must utilize a compromise or balance of properties in order to achieve objectives or goals in the preparation of film forming materials.